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Appendix A: How the U.S. Preventive Services Task Force Grades Its Recommendations

Guide to Clinical Preventive Services, 2012

The U.S. Preventive Services Task Force (USPSTF) assigns one of five letter grades (A, B, C, D, or I) to each of its recommendations to describe the recommendation's strength. In May 2007, the USPSTF changed its grade definitions based on a change in methods and, in July 2012, it updated the definition and suggestions for practice for the grade C recommendations.

Describing the strength of a recommendation is an important part of communicating its importance to clinicians and other users. Although most of the grade definitions have evolved since the Task Force first began, none has changed more noticeably than the definition for a C recommendation, which has undergone three major revisions since 1998. Despite these revisions, the essence of the C recommendation has remained consistent: At the population level, the balance of benefits and harms is very close, and the magnitude of net benefit is small. Given this small net benefit, the Task Force has either: not made a recommendation “for or against routinely” providing the service (1998); recommended “against routinely” providing the service (2007); or recommended “selectively” providing the service (2012). Grade C recommendations are particularly sensitive to patient values and circumstances. Determining whether or not the service should be offered or provided to an individual patient will typically require an informed conversation between clinician and patient.

Grade Definitions After May 2007

What the Grades Mean and Suggestions for Practice

With the USPSTF's 2007 updates to grade definitions, suggestions for practice are now associated with each grade. The USPSTF had also defined levels of certainty regarding net benefit. These definitions apply to USPSTF recommendations voted on or after May 2007.

Grade

Definition

Suggestions for Practice

A

The USPSTF recommends the service. There is high certainty that the net benefit is substantial.

Offer or provide this service.

B

The USPSTF recommends the service. There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial.

The USPSTF recommends against routinely providing the service. There may be considerations that support providing the service in an individual patient. There is at least moderate certainty that the net benefit is small.

Offer or provide this service only if other considerations support the offering or providing the service in an individual patient.

D

The USPSTF recommends against the service. There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits.

Discourage the use of this service.

I Statement

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality, or conflicting, and the balance of benefits and harms cannot be determined.

Read the clinical considerations section of USPSTF Recommendation Statement. If the service is offered, patients should understand the uncertainty about the balance of benefits and harms.

* The USPSTF voted on the following definition of Grade C in July 2012. The new definition, voted while this Guide was in final production, does not apply to any of the recommendations in this Guide. Grade Definition: The USPSTF recommends selectively offering (or providing) this service to individual patients based on professional judgment and patient preferences. There is at least moderate certainty that the net benefit is small. Suggestions for Practice: Offer or provide this service for selected patients depending on individual circumstances.

Levels of Certainty Regarding Net Benefit

The available evidence usually includes consistent results from well-designed, well-conducted studies in representative primary care populations. These studies assess the effects of the preventive service on health outcomes. This conclusion is therefore unlikely to be strongly affected by the results of future studies.

Moderate

The available evidence is sufficient to determine the effects of the preventive service on health outcomes, but confidence in the estimate is constrained by such factors as:

As more information becomes available, the magnitude or direction of the observed effect could change, and this change may be large enough to alter the conclusion.

Low

The available evidence is insufficient to assess effects on health outcomes. Evidence is insufficient because of:

The limited number or size of studies.

Important flaws in study design or methods.

Inconsistency of findings across individual studies.

Gaps in the chain of evidence.

Findings not generalizable to routine primary care practice.

Lack of information on important health outcomes.

More information may allow estimation of effects on health outcomes.

* The USPSTF defines certainty as "likelihood that the USPSTF assessment of the net benefit of a preventive service is correct." The net benefit is defined as benefit minus harm of the preventive service as implemented in a general, primary care population. The USPSTF assigns a certainty level based on the nature of the overall evidence available to assess the net benefit of a preventive service.

Grade Definitions Prior to May 2007

The definitions below (of USPSTF grades and quality of evidence ratings) were in use prior to the update in methods and apply to recommendations voted on by the USPSTF prior to May 2007

A — Strongly Recommended: The USPSTF strongly recommends that clinicians provide [the service] to eligible patients. The USPSTF found good evidence that [the service] improves important health outcomes and concludes that benefits substantially outweigh harms.

C — No Recommendation: The USPSTF makes no recommendation for or against routine provision of [the service]. The USPSTF found at least fair evidence that [the service] can improve health outcomes but concludes that the balance of benefits and harms is too close to justify a general recommendation.

D — Not Recommended: The USPSTF recommends against routinely providing [the service] to asymptomatic patients. The USPSTF found at least fair evidence that [the service] is ineffective or that harms outweigh benefits.

I — Insufficient Evidence to Make a Recommendation: The USPSTF concludes that the evidence is insufficient to recommend for or against routinely providing [the service]. Evidence that [the service] is effective is lacking, of poor quality, or conflicting and the balance of benefits and harms cannot be determined.

Quality of Evidence

The USPSTF grades the quality of the overall evidence for a service on a 3-point scale (good, fair, poor):

Fair: Evidence is sufficient to determine effects on health outcomes, but the strength of the evidence is limited by the number, quality, or consistency of the individual studies, generalizability to routine practice, or indirect nature of the evidence on health outcomes.

Poor: Evidence is insufficient to assess the effects on health outcomes because of limited number or power of studies, important flaws in their design or conduct, gaps in the chain of evidence, or lack of information on important health outcomes.